This invention relates to bolts. It has particular application to bolts used in anchor bolt assemblies of the type which have expandable sleeves.
In some applications where the length of a bolt cannot be viewed steps must be taken to assure building inspection authorities that bolts of the right dimensions have been used to satisfy the regulations relating to a particular application. For instance, in the mounting of lift well guide rails, the building regulations require that bolts supporting the rails must extend for a prescribed length into the concrete wall forming the well. At present, the only sure method of ensuring that the bolts extend the full prescribed distance into the concrete is to tie the ends of the bolts to the concrete reinforcing bars prior to pouring the concrete. In this method where the bolts are cast-in there is a considerable problem in achieving correct positioning of bolts and frequently it is difficult to obtain correct alignment with the guide rails they are to support.
A more desirable method of positioning these bolts would be to drill the concrete after casting and inserting bolts having a known form of expandable means on their ends to set them in their correct positions. Unfortunately, at present, the inspection authorities have no way of determining whether the correct size of bolt of this type has been used and whether it has been set correctly in the concrete, and, consequently, it is not possible to use this method.